The present invention relates to devices positionable in body cavities for treatment or viewing and in particular to angioplasty catheters, especially for coronary and peripheral arteries.
Balloon catheters are well known for their utility in treating certain types of obstructions or occlusions in blood vessels, such as plaque build up. Angioplasty catherization typically involves aligning a balloon catheter within the vessel to position its dilatation balloon at or along the obstruction. Then, fluid under pressure is supplied to the balloon through a balloon inflation lumen in the catheter, expanding the balloon against the obstruction.
Balloon angioplasty catheters have been around since the late 1970s. Since that time the efficacy for the procedure has not significantly been improved. The restenosis rate for PTCA (angioplasty) has always averaged about 40 percent. Overinflation of the balloon can cause cracks in the intimal layer of an artery, allowing smooth muscle cell proliferation. Furthermore, overinflation of the balloon is a major cause of restenosis. In extreme cases, an aneurysm or perforation of the vessel can result from overinflation.
Overinflation of balloon catheters arises from several factors. One factor is the variety of plaque hardnesses. Atherosclerotic disease in an artery can result in plaque deposits having a wide range of hardness from xe2x80x9cscrambled eggsxe2x80x9d to bone. Another factor is that the profile of the obstruction is generally eccentric within the artery and does not conform to the concentric dilatation balloon profile. The physician can monitor the pressure on the inside of the balloon, but not the pressure between the outside of the balloon and the inside wall of the artery. As a result, overinflation can occur because of the concentric configuration of the balloon and the inability to assess the pressure between the outside of the balloon and the inside wall of the artery. The fluid pressure inside the inflating balloon cannot alert the physician to excessive pressure between the external surface of the balloon and the arterial wall.
The application of heat to the vessel wall during the angioplasty procedure appears to have a positive effect by requiring less force to compress the plaque against the arterial wall. Conventional balloon catheters do not provide an effective means for heating vessel walls during an angioplasty procedure. Stents are also employed in arteries. However, it is difficult to determine when the stent has been fully deployed and is in contact with the vessel wall. Current angioplasty catheters do not provide a reliable means for the physician to determine if a stent is fully deployed.
Therefore, it is an object of the present invention to provide an angioplasty balloon adapted to allow a physician to conform the balloon to an artery""s inner profile, and further avoid overinflation of the balloon.
Another object of the present invention is to provide an angioplasty catheter with individually inflatable dilatation compartments that allow the balloon to assume an eccentric shape and apply different localized pressure to the different regions of surrounding artery.
A further object of the present invention is to provide a angioplasty catheter with pressure sensing capability on the balloon""s external surface for monitoring pressure between the balloon and artery tissue allowing the catheter to be adaptable to treat different plaque hardnesses and to avoid overinflation.
Another object of the present invention is to provide a angioplasty balloon catheter which may be utilized for deployment of a plastically deformable stent and for controllably expanding the stent toward a custom fit to an eccentric arterial profile.
Yet another object of the present invention is to provide an angioplasty balloon catheter having thin film heaters on the outside of the dilatation balloon to allow the physician to heat the obstructed area during the angioplasty procedure, or to deploy and expand recovery metal stents by locally heating a treatment site within an artery.
A further object of the present invention is to provide an angioplasty balloon catheter with film transducers on the balloon""s external surface to provide a means of intra vessel imaging.
Still another object of the present invention is to provide an angioplasty balloon catheter with perfusion lumens extending through the catheter shaft with a port located adjacent the proximal end of the balloon and another port located adjacent the distal end of the balloon, thereby allowing fluid to flow past the catheter when the balloon is expanded and in contact with the arterial inner surface.
Yet another object of the present invention is to provide dual balloon angioplasty catheter with distal balloon opening the occlusion and the proximal balloon for deploying a stent, intra vessel ultrasonic imaging or delivering a drug to the lesion site.
To achieve these and other objects there is provided a device for performing a balloon angioplasty procedure. The device includes an elongate catheter having a proximal end and a distal end. A dilatation balloon is fixed to the catheter tubing near the distal end and extends substantially longitudinally along the catheter tubing. The catheter is flexible and maneuverable with a guide wire to locate its distal tip within a body lumen and place the dilatation balloon within the obstructed area. Radiopaque markers on the catheter shaft under the working area of the balloon assist in positioning the balloon in the artery.
The balloon has a plurality of dilatation compartments adjacent one another and arranged angularly about the catheter tubing. Fluid under pressure is individually supplied to the various dilatation compartments. Each compartment is fluid tight and isolated from the other compartments. The balloon dilatation means which supplies the fluid under pressure to the various dilatation compartments is controllable to alter the dilatation pressure to a value different than the nominal pressure in at least one of the compartments while maintaining the dilatation pressure at the nominal value in a second selected compartment. This allows the physician to controllably alter the balloon profile away from the nominal shape and toward conformity with the tissue wall profile of the tissue wall segment.
The catheter tubing additionally may include at least one perfusion lumen open to the exterior of the catheter tubing at a first and second locations proximal and distal relative to the balloon, respectively. When the balloon is dilated into surface engagement with the surrounding tissue wall segment, it prevents passage of fluids along the catheter tubing. Thus, the perfusion lumen allows fluid passage during the angioplasty procedure.
The balloon catheter can include a pressure sensing means mounted on the exterior wall of the balloon, to measure the pressure between exterior surface of the dilatation balloon and the tissue wall segment. Preferably, the pressure sensing means includes a plurality of piezoelectric pressure transducing thin films or fluid filled pressure sensing tubes. A piezoelectric pressure transducing thin film or fluid filled pressure sensing tube is preferably bonded to each outer wall of the dilatation compartments. The pressure sensing means is coupled to a power source at the proximal end. A display means is operably connected to the sensors to display the pressure between the artery wall and the balloon""s exterior surface.
The balloon catheter additionally can have thin film heating elements on the outside of the balloon surface. These are preferably bonded to the outer wall of each dilatation compartment and are connected to a power source and display means at the proximal end of the catheter. The temperature may be monitored and adjusted during the angioplasty procedure to heat adjacent tissue or deploy a stent formed of a recovery metal or thermoset plastic.
The balloon catheter additionally may include piezoelectric ultrasonic transducers on the balloon""s exterior surface allowing the physician to utilize ultrasound to position the catheter and to view the vessel surface surrounding the catheter. The piezoelectric thin film transducers used as pressure sensors also can be alternatively used as ultrasonic transducers. The piezoelectric thin film transducers are coupled to a control which adjusts the signal to films for pressure sensing or ultrasound imaging.
Another embodiment of the balloon catheter incorporates two balloons at the distal end of the catheter. The first balloon on the distal end is utilized to enlarge the occluded area. The second balloon, located just proximally from the distal balloon, can be utilized for stent deployment or drug delivery. The drug delivery portion of the balloon is indented and perforated. The two balloons can employ the pressure sensors, ultrasonic transducers and heating elements on their exterior surfaces. Radiopaque marks are located on both balloons or between to allow the physician to position the balloons in the occluded area.